Approximately 75 percent of all drugs marketed in the United States are not approved for use in Children. This problem is especially apparent for the youngest children and for those with diseases that are uncommon, either in absolute terms or relative to the frequency observed in the adult population. To address this issue, the Network of Pediatric Pharmacology Research Units (PPRU) was formed. The objectives of this specific proposal are: 1) to facilitate completion of clinical trials involving both pre- and post-marketed therapeutic agents by bringing experienced pediatric clinical pharmacologists in a supportive research environment together with a large number of primary and specialty pediatricians who provide medical care for a large and varied pediatric population; 2) to gather the necessary clinical data that will permit labeling of drugs in children of all ages; 3) to conduct research on new therapeutic modalities and new outcome measures, especially in the areas of hypertension and asthma; 4) to examine the effect of development on enzymatic systems responsible for biotransformation of drugs in children; and 5) to provide a teaching environment where health care professionals from a variety of backgrounds can learn about all aspects of pediatric pharmacology and can gain experience in the conduct of clinical trials in children. To accomplish these objectives, previous experiences and necessary functions were reviewed. A detailed organizational structure and standard operating procedures were developed to meet all of the goals outlined above. Most of the components to meet the objectives have been previously implemented. To meet specific objectives 3 and 4, two new projects have been developed and are presented in this proposal. In addition, mechanisms for integration with other sites to form an efficient collaborative network are addressed. Ultimately, the proposed unit will play a key role in improving therapeutics for children by collaborating with other units to achieve the primary mission of increasing the number and variety of drugs labeled for use in children.